Apparatus for testing side seams of containers



D. G. MAGILL.

Aug. 30, 1960 APPARATUS FOR TESTING SIDE SEAMS OF CONTAINERS Filed Oct. 24, 1955 INVENTOR.

DONALD G. MAGlLL M WM ATTORNEYS Patented Aug. 30, 1960 APPARATUS FGR TESTING SIDE SEAMS OF CONTAINERS Donald G. Magill, Great Neck, N.Y., assignor to American Can Company, New York, N.Y., a corporation of New Jersey Filed Get. 24, 1955, Ser. No. 542,320

4 Claims. (Cl. 73-88) The present invention relates to apparatus for testing the rupture strength of side seams of pressure containers and has particular reference to such apparatus in which the pressure action of certain products packed in the containers may be simulated.

In the packaging of certain products which must be maintained under internal pressure, such as preleavened dough prepared for home baking, it has been found that containers having a pull type lap seam and made of fibre material are best suited for this type of product since they permit of easy opening and removal of the dough without sticking. Containers carrying preleavened dough must also be held under refrigeration and are subject to humid conditions.

It is therefore a requirement of such containers that their side seams be mechanically strong enough to withstand the internal pressure of the product under various temperature and moisture conditions and yet be weak enough to permit of easy opening by pulling the overlapped layers apart to free the product without disintegration. In order to insure that such side seams are of proper strength, they are frequently tested during manufacture of the containers. However this testing is difiicult to effect without some means of simulating the pressure action of the product after it is packed in the container.

An object of the instant invention is the provision of an apparatus for pressure testing the side seams of empty containers wherein the internal pressure created by a product after packing may be readily simulated in the empty containers so that proper testing of the side seams may be effected.

Another object is the provision of such a testing apparatus which is designed to hold a desired internal pressure on the inner face of the container in such a manner as to permit opening of the container as efiected by the consumer so as to test the side seam for proper opening.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description, which, taken in connection with the accompanying rawings, discloses a preferred embodiment thereof.

Referring to the drawings:

Figure l is a perspective view of a composite fibremetal pressurized container of the character to be tested in a testing apparatus embodying the instant invention;

Fig. 2 is a longitudinal sectional view of a testing apparatus embodying the instant invention, the view showing the body of the container illustrated in Fig. l, in testing position on the apparatus, parts being broken away; and

Fig. 3 is a fragmentary sectional view similar to Fig. 2, the view showing the container shown in Fig. 1, with its end closures cut away, in position on the apparatus for testing.

As a preferred or exemplary embodiment of the instant invention the drawings illustrate an apparatus for simulating in an empty biscuit dough container A (Fig. 1), an internal pressure as created in a filled container, so as to test the container for bursting strength and for proper opening.

The container A preferably is a cylindrical composite container having a fibre material body B and sheet metal end closures C, permanently secured to the ends of the body in suitable end seams D, preferably of the double seam type in which flange portions of the body and the end closures are interfolded. The body B preferably is made from a single rectangular shaped blank having opposed marginal edge portions overlapped and adhesively secured together to provide a double layer side seam B (see also Figs. 2 and 3) extending substantially the full height of the body.

In order to open the container A, the outer overlapped side seam marginal edge portion of the body is provided with a pull tab P (Fig. l) which extends beyond the side seam E, on the outside of the body and is free for easy gripping by the consumer to pull the tab outwardly and thus separate the layers of the side seam. The tab F extends the full length of the side seam E and when pulled to break the side seam, also tears the body circumferentially adjacent the closure end seams C to lay the container open for the easy removal of the biscuit dough contained therein.

The biscuit dough disposed in the container A contains a leavening agent which generates a gas which expends the dough in the container and builds up considerable pressure therein. The side seam E is designed to withstand this pressure. On the other hand, the pressure built up within the container is utilized to assist in the easy opening of the side seam by use of the pull tab F. In this connection the internal pressure explodes the side seam E just prior to the complete separation of the layers of the side seam when pulled apart by the pull tab F and this explosion effects a clean breaking apart f the layers. It is to the testing of these desired qualities in the side seam E that the testing apparatus of the instant invention is directed.

The testing apparatus preferably comprises a cylindrical, soft rubber flexible testing tube 11 (Figs. 2 and 3) having an outside diameter or perimeter slightly smaller than the inside diameter or perimeter of the contm'ner body B and having a length slightly longer than the body B. The ends of the tube 11 are permanently closed with two rigid end members 12, 13 in any suitable airtight manner, as for example by a wire clamp 15 which presses the marginal end portions of the tube into a groove 16 formed in the periphery of the end members, as shown in the drawings.

The two end members 12, 13 are tied together in spaced and parallel, fixed relation, by a plurality of rods 18 which extend through the space inside the tube 11. The ends of the rods 18 are reduced in diameter to provide a shoulder against the inner faces of the end members. These reduced diameter portions of the rods 18 extend through the end members 12, 13 and carry lock nuts 19 outside the end members to unite the end members and i 3 the rods in arigid unitary structure for the soft rubber tube 11.

The interior of the tube 11 between the end members 12, 13 constitutes a pressure chamber 2.1 into which a fluid pressure medium such as compressed air is introduced to expand the tube for testing of the containers. For this purpose the end member 12 is provided with an aperture 22 which communicates with the pressure chamber 21. The aperture 22 is threaded and carries a fitting 23 on one end of a flexible pipe 24. The opposite end of the pipe connects with a maximum reading type pressure gauge 25. The gauge 25 in turn is con.- nected to a pipe 26 which lea'ds from a suitable source of compressed air. A two way valve 27 havinga vent 23 to the atmosphere is .connected into the pipe 26 to control the air introduced into the pressure chamber 21.

Testing of the side seam E of a container A may be elfected both before -or after the end closures C are seamed onto the. body B. Where the body B alone, without its end closures C, is to be tested, the body is slipped over the soft rubber tube 11 so that it surrounds the tube as shown in Fig. 2. The valve 27 is then turned to introduce compressed air into the pressure chamber 21, by way of the gauge 25 and flexible pipe 24. The air thus introduced into the chamber 21 expands the testing tube 11 until it fills the container body B in the same manner and in simulation of the expanding action of preleavened biscuit dough in a sealed container, the testing tube 11 being forced outwardly against the inner surface of the container body B with a uniformly dis tributed pressure as best shown in Fig. 3.

Two tests usually are performed on container bodies of this nature. In one test, the pressure created in the container body by the introduction of compressed air into the pressure chamber 21 is permitted to build up until the side seam is ruptured. The rupture pressure, i.e. the maximum pressure built up before rupture occurs, is indicated on the gauge 25. V This test is performed to determine the maximum strength of the side seam of the a container, for comparison with the known pressure created by the biscuit dough when sealed in a container. Through this test, performed periodically on random selected containers during their manufacture, a close check may be had on the strength of the side seams of the containers to insure a suflicient margin of safety.

In the second test, the ease of opening the container is determined. In this test, sufl'icient compressed air is introduced into the pressure chamber 21 to create a pressure substantially equal to that known to be generated by the biscuit dough in a sealed container. This pressure, as indicated on the gauge 25, when reached, is held constant while the flap or tab F adjacent the side seam is pulled to break open the seam. The manner in which the seam breaks and the ease with which it breaks is thereby determined.

When such tests are to be performed on bodies B having end closures C attached thereto, the panels of the end closures are cut out so as to leave the end seams D attached to the bodies, since it is the end seamseand not the closure panels that afiect the strength of the side seam and the ease with which it is broken to open the container. With the panels of the closures removed as shown in Fig. 3, the container may be readily slipped over the testing tube 11 as shown in Fig. 3 to perform the tests in the same manner as in testing the body alone. After testing, the pressure created in the pressure chamber 21 is dissipated by turning the valve 27 to exhaust the air through the vent 28 so as to remove the body B from the testing tube 11.

Hence, with such a testing apparatus, pressures generated by products in sealed containers and, exerted against the side walls of the containers to affect the side seams, may be readily simulated in an expeditous manner for inspection purposes during the manufacture of the containers to insure that the containers have side seams strong enough to hold the product and still be constructed so that they are readily broken by the consumer to open the containers. It should be noted in this connection that the instant apparatus is not intended to test the pressure on the end closures of the container since such end closures have no influence upon the side seam under discussion.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

I claim: 1. An apparatus for testingthe rupture strength of side seams of open ended cylindrical container bodies, comprising in combination an inflatable cylindrical tube having an outside perimeter slightly smaller than and substantially conforming to the inside perimeter of a said container body, the length of said tube being not less than about the length of said body, means for sealing the open ends of said tube along marginal circumferential portions thereof spaced apart a distance sufficiently greater than the length of said body to leave said marginal portions extending beyond said body as the latter is tested, means for inflating the sealed tube, and means for indicating the pressure in the inflated tube, whereby said tube when deflated is insertable to substantially coextensive relation within said body and inflation of the tube by said inflating means to apply substantially uniform and increasing pressure against the full inside perimeter thereof is effected until the rupture strength of the'body side seam is shown by said pressure indicating means when said seam is ruptured by the pressure applied by the inflated tube.

2. An apparatus for testing the side wall structure of a tubular container body, comprising in combination an elongated flexible testing time having a length slightly greater than the length of the body of a container to be tested and an outside perimeter slightly smaller than and substantially confonning to the inside perimeter of said container body for complete insertion into said body, a pair of rigid end members for said tube spaced apart a distance greater than the length of said body and secured to the ends of said testing tube to seal the same along marginal circumferential portions thereof spaced apart a distance sufficiently greater than the length of said body to leave said marginal circumferential portions extending beyond each open end of said body, and means for introducing a fluid pressure medium at controlled pressure into said testing tube to expand it uniformly into engagement with the inner surface of said container body and to apply pressure thereagainst in simulation of pressure generated by a product when sealed in a said container body to test the effect of such pressure on the structure of said body.

3. An apparatus of the character defined in claim 2 wherein said rigid end members are retained in their spaced relationship by at least one rigid member disposed within said tube.

4. An apparatus for'testing the side wall structure of a tubular container body having closures united by end seams to the open ends thereof, central portions of said closures being removed leaving only end seam portions thereof on the container body for the purpose of testing, said apparatus comprising in combination an inflatable tube having an outside perimeter slightly smaller than and substantially conforming to the inside perimeter slightly smaller than and substantially conforming to the inside perimeter of a said container body to be tested, the length of said tube being slightly greater than the length of said body, a pair of rigid end members for said tube spaced apart a distance greater than the length of said body and sealed to the ends of said tube along marginal circumferential portions thereof spaced apart a distance sufliciently greater than the length of said body to leave said marginal portions of the tube extending beyond said end seam portions of the body during testing, and means for inflating said tube to expand uniformly into engagement with the inner surface of said body and to apply pressure thereagainst, in simulation of the pressure applied to the interior of a sealed container body by its contents, to test the efiect of such pressure on the structure of said container body.

References Cited in the file of this patent UNITED STATES PATENTS Johnson Apr. 5, 1904 Campbell June 24, 1930 Svirsky Oct. 20, 1942 Grant et a1 Feb. 25, 1947 Henderson Sept. 6, 1949 Stillinger May 9, 1950 Aubrey et a1 Dec. 11, 1951 FOREIGN PATENTS France Ian. 16, 1929 

